Well bore electrical generator



June 7, 1960 l.. YosT ETAL 2,940,039

WELL BORE ELECTRICAL GENERATOR Filed June lO, 1957 3 Sheets-Sheet 1 INVENTORS Loro ros? ,f w/L/AM R. W/Lso/v RA rfv/C050 ya EAR y /BY I I f /ATTORNEY June 7, 1960 L.. YosT ETAL wELL EoRE ELECTRICAL GENERATOR 5 Sheets-Sheet 2 Filed June l0, 1957 INVENTORS .LLOYD yosT WILL/AM R. W/LSON RAVMOND- MCCREARV FIGZB June 7, 1960 L. YosT ET AL 2,940,039

wELL EoRE ELECTRICAL GENERATOR Filed June 10, 1957 3 Sheets-Sheet 3 IN NTORS L0 y T W/LL M R, W/L 50N RAY/wo DWC REARV BY van e ATTORNEYS WELL BORE ELECTRICAL GENERATOR Lloyd Yost, San Gabriel, William R. Wilson, Glendale, and Raymond A. McCreary, North Hollywood, Calif., assgnors, by mesne assignments, of one-half to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of New York and one-half to California Research Corporation, San Francisco, Calif., a corporation of Delaware Filed June 1o, 1951, ser. No. 664,69s

s claims. (ci. 324-70) The present invention relates to turbo drill speed indieating devices and more particularly to tachometer generator apparatus for measuring the speed of rotation of a hydraulic turbine coupled to a drilling bit.

The present invention has for an object the provision of a compact speed indicator of the tachometer generator type that may be directly coupled to the drive shaft of a borehole hydraulic turbine wherein the rotor comprises an annular permanent magnet member directly coupled to the turbine driveshaft, the magnet member being rotatable about a cylindrical stator member isolated from the drilling iluid used to drive the hydraulic turbine.

In the drilling of an earth bore with a drill rotated by a hydraulic turbine supported on the lower end of a drill pipe, the combination known in the art as a turbo drill, the motive iluid is a conventional formulation of drilling Huid supplied under high pressure to drive the turbine unit. In the preferred form of such turbo drill units, the drill bit is coupled directly to the drive shaft of the turbine unit and the turbine itself includes a plurality of stator and motor stages that use the high pressure drilling lluid to turn the turbine shaft and the drill bit. In such drilling, it is common to rotate the drill pipe at a low speed either in the same direction as the drill bit is turning, or the drill pipe is allowed to rotate slowly in the reverse direction due to reaction torque between the turbine rotor and the turbine housing supported on the drill pipe. This rotation prevents sticking of the drill pipe. However, such rotation of the drill pipe is in general substantially independent of the speed of rotation of the turbine shaft. While it has been suggested that such reaction torque between the drill bit and the drill pipe be used as a measure of the speed of rotation of the drill bit, any resistance such as that produced by drag between the drill pipe and the side of the well bore prevents the resultant reaction force from being a true measure of the rotational torque between the drill bit and the supporting drill pipe.

Another proposal has been to use apparatus for varying the ow of drilling fluid between the earths surface and the turbine unit in accordance with ythe speed-,of rotation of the turbine shaft. Such apparatus of course requires some type of restricting mechanism such as an orilice that is opened and closed to change the pressure of the drilling uid. The resulting ow Variations create I pulses, but these must be of suiiicient amplitude and duration as to be distinguishable from minor pressure variations normally present Vwhere conventional high pressure reciprocating mud pumps supply the drilling liuid to the turbine. Such apparatus, of course, requires sensitive pressure measuring apparatus to be used within the drill pipe or connected thereto at the earths surface. This type of system inherently transmits information only periodically and slowly. Well bore signalling systems using electrical current transmission have been proposed for transmission of other data, but, unfortunately, such systems have not had ecient signal generating systems capable of generating maximum current in the confined space available in a drill pipe of conventional diameter.

In accordance with the present invention there is provided a system for etliciently generating an electrical signal of varying frequency corresponding to variations in thespeed of rotation of the turbine drill shaft, which can be transmitted by kany of several diferent electrical transmission systems, to permit detection of the speed of rotation at the earths surface on a continuous and instantaneous basis. The speed of rotation can thus be indicated to the driller, for example by a frequency meter connected to the signal receiving system.

While electrical signal generators have been proposed heretofore in various well-signalling or well-surveying operations, the present invention permits maximum signal current to be generated in a minimum of space and with minimum problems in insulating the electrically conducting portions of the generator. In accordance with the invention,the electrical winding is compacted into an elongated cylindrical stator member of suiciently small diameter that it can be positioned in the central portion of the drill pipe supplying drilling fluid to the turbine. In one embodiment, the winding comprises an elongated flat strip of conducting material, wound in a generally elliptical form around a laminated magnetic core Whereinthe elongated axis of said ellipse is substantially coaxial with lthe drill pipe. Each turn of the strip conductor is insulated so that said winding is continuous over the stator laminations, and said stator laminations are stacked so that their faces are substantially perpendicular to the axis of the drill pipe. Said stator assembly is desirably potted in a pressure-sealed cylindrical can member, so that said stator may withstand hydraulic pressure vof the drilling uid wherein it is located. Further, in accordance Vwith the invention, the rotor of the tachometer generator is coupled directly -to an upward extension of the turbine drive shaft and includes a permanent magnet member of substantially annular form, having two or more poles, with the permanent magnet member of said rotor positioned so that upon rotation of said annular rotor in the, drilling tluid and around the cylindri. cal stator, there is generated an alterating current whose frequency is proportional" to the speed of rotation of the rotor member and, consequently, of the'turbine shaft.

In an alternative form of the invention, the continuous conductor lforming the winding of the generator is a generally square or rectangular wire insulated so that the rectangular spaces formed on opposite sides of the laminations are eincently illed and the volume above said spaces that completes the cylinder can also be filled more completely.

Further objects and advantages of the present invention will become apparent from the following detailed spec' cation, taken in conjunction with the accompanying drawings, which form an integral part of the present application.

Fig. v1 is a vertical schematic view, illustrating one method of transmitting the electrical signal generated in response to the rotation of the turbine by the electrical generator of the present invention;

Fig. V2A is a longitudinal'view, partially in section,

through the upper part of the electrical generator of the I of square cross-section.

Referring Vnow to the drawings. and in particular to ly Y such construction can beachieved onlywith' greaty dili-d culty. However, current will leave the Velectrode 21 in a direction perpendicular to its surface, and follow aV ycured (not necessarily circular.) path back to drill pipe i4, as indicated by lines ofcurrent flow A. The longer the insulatcdsection.aboveand. below shell 21, thexgreate'r will be the resistance of thecOnductingpaths shunting.,

1 thegeneratedjsignal. Theonly useful signal current is turbinezunit lll-applied' toL/thejspipethrough the housing.

Motive power for;tur.bine,10.1issuppliedlby drilling iluid' pumped under high pressure; fromthe earthssurface' througlrdrill, pipe 1.4'. The1drillingfid1 desirablyl is -conthat Vwliiclifriins near. theA earths.. surface as indicated. by lines offcurrent flow'A, andsis intercepted lbetween ground electrode. 2.4i and drill pipe 14: Thus, theelectrica1-po tential appearing 'betweeri drill [pipet 14; and: ground; elecftrode 24, includes the signal from the tachometerf genventional .int formulation. with-aibase` of'water, oil, voran emulsion. The; drillinguidznot'only supplies power for the turbine, unit llL/but also acts to'fcooland lubricate drillbit l1, flush:cutti1gsfrom the bottom ofwell'bore! that will exceednormal fluid pressures in earth forma- Thev drillingfluid is` l2, andA providea` hydrostatic: pressurein theV well 'boretionsv penetrated; byV the well .boref normally desanded', thatis,.thei.chips.of rock, sand-and other granularY materials 'areremovedfromthe drilling lluidafter itis returned .from the' borehole; butaeven with .the best of commercial` desanding equipment, the drillingiluidcontains. aconsiderab1e.:amount'of` granular mate# rial.. Additionally, the: drilling.'V fluidf maycontainlostV circulation-remedial. material*- toprevent loss-of drillingj'v fluid. to low pressure formations along the-well b'oreay This materialfis. generally fibrous or` ake-like. Thus,

erator. Thispotential is ampliiiedandltered, thus separating the signal from other potentials. The frequency of the signal is indicated by theiv combinationfof arn-y plier 26 Aand frequency meter 28, 4so that there is presentedfat the earths surface a^ direct indication, not

only thatfdrill'bit 11"is`rotating, butthe speed atwliicltlI it is rotating.' Frecnxencyv meter 28`will ofi-course becalibrated in revolutions perA minute yso that a'driller. is continuouslyV giver-ran 4indicationl of thegspeedofthe drill the drilling fluid, containsia. considerable amount-of par- Y ticulate material of varioussortsgjwhen circulatingin thedrilling operation..l Y I ,n Y .Y

The particulate Amateriak in :the-.drilling iluidk can' easily stop circulation throughrthe drill'` pipeaswell as `-irr the well boreif small passagesof unduly restricted {iow-Y paths are presentin'thee circulation.system. Excessive contact pressure between drill:v bit "112 and'the earth formationv beingl drilled'..maysalso. stall the turbine, 'asf might alsoother conditions. Therefore, one; ofthe pri- The arrangement of' Fig.l 1- illustrates `one-methodl of transmitting information generated"l by' thetachometer generator.4 However, several other methods of`transmitting the electrical sig'nal' itself will beJ discussed here 1 inafter: V Y v Y Figs.I 2A and 213gy illustrate lone embodiment of the tachorneter generator and" reference isr` now made to Vthese iigures for avv complete description thereof. As indi` catedf in the lowerj partof'Fig. 2B, turbine drive shaftlStfh'asmounted-thereonaplurality of rotor vanes 32;. Y each offwhich'eooperateswith` a set-ofi statorvanes 34'- rnountedin and secured`tohousing 37. HousingA 37"inA turn is suppertedfrom-the lower end of drill pipe 14? by generator housing 36;

mary, problems.'` inzdrllingi withv aturboA drilliof the ytype` shown. in Fig.. l, lies in thenecessity forfknowingL Yin-I stantaneously and continuously the speed'ofl rotation'of the-turbine rotor andthe drilllbit 11 on bottom; AWhen Vthe turbine-.andthedrill bit reach a depthV ofgreater than 1G00 tof2000 '.feet, themethod.of"transmitting4a signal V from, the drill bit` to. the4 earths surface-using eitherv a sonic generator, pressurefyaryingnorfother similar lsysy tems, results either. in slow. transmissionoff the signalfor virtually no. signal.' at .all to the' earths surface.

inl then present invention, ...theretis provided:V apparatusy for generating a substantial electrical signal thatl can be transmitted-and receivedlfrom' depths greatly-vl in excess, of thev lowerlimitation of: previously known methods.

Inorder- 'to-reduce anyv hydraulic friction as much aspossible; it is'; desirable that the speed detectingdevicebe as compactas possible; to assure'maximumxflowV area through thev conductor pipe.-

compact formwithinthecenter of; and's'ubstantially coaxialwith, theturbine housing and drill pipe.

thev outside offannular rotorltl, canl be madeY sufciently l large softh'at there is minimum pressure; drop due to As indicated'schematically.inthefarrangement'offFig: 1,

anv electrical. signal generated by tarchomete'r-`U generator' 17 is connected to a borehole antenna system, including. an elongated. transmission orantennaV sectionf20 l that surroundsdrill pipe 14! andl is'zinsulated therefrom by a Sleevemember 22 which: also eXtends-.aVv substantial dis-V tan-:e both above and. below the` antenna sectionkv 20';-

Desirably sleevernexnberv 22 is made of ai durablejinsulat- Yin?V material, such asV rubber: vulcanized'to'one ormore p sections ol' a heavy-walledV pipe known'` inf'theA arti as drill collar. In thiszway,rsectionr22 canibe included in drill. string; 1:4I directly above` turbine unit 101 tofprovide shell 2l;A and generator. 1'71 is .through wire 23. Y

YElectrical contactf withfearth is substantially,proportional to the axial length of antennaiscct-ion'li Ideally,

this' sectioni wouldn.extenditolftheav earths=v surface, but

flow' through Y said pasageway;

that-v supports rotor *4011 in: bearing-member V59 mounted in the=centerof housing 361011 Vtiri members458.

As indicated generally in- Eig.v 2B, rotor element 40 comprises an' annular rpermanent'rnagnetn element"V 48;AV and ismountedffor direct-rotationby *turbine shaft30 through a vpair'M ot.,d rive'pinsA 49' passingjfrom couplingrnemberY Y 50 into th'eiupper-end:of=shaft30; vShaft/3,0 and'coupling1 Y 50` are secured together -by` stud and 1 nut arrangement 52: Couplingvtisfformed las'an` upturnedcup member 51 having a Islotl *53j milled'. therein` that forms a vertically exible'drive *connectionV with thejdrive` key 54 directly the. required weight Von' drill. bitfll. As illustrated inl n Fig. l, antenna section 2l) may 4beason'iewhatireduced` in diameter where. a metallic. shells21 overliesthe bonded` rubber portion. VThe interconnection' between antenna connected torrotorrnernber'tl The inner surface of slot` 53l has rubberv covered surfacing 55j to absorby vibration. in-the drive mechanism;Y Af circular shell 57ihol'ds. the.Y

sides of slot 53 against loutwardexure.

Referring n0.w` to .thegspeciiic 'construction of.VA stator member 42 rofrour ,in'sideeou generator, it will benoted thatV the statorcomprifsesfa plurality Vof laminations 601 stacked-sorthatj their facesl areperpendicular to` the. axis*A oftheegeneratorhousing, turbine,l and'drill pipe.v These Inaccordance with theV present invention; a maximumY ow, area aroundtachoma.` eter.: generator; 17fjis`y preserved bypforming the-uint 1n a In this'` way, theffanriular'v flow passageway, Yindicated as38; around Further, in accordance` with-the--inventiom the stator' elementV 42 is positioned; astheA-innermost 'portion' ofeth'e-tachometer generator and is' supported concentrically with the-housingt'by ahead A supporting member'y 44'- mounted on a plurality of n` v members'46'forming Aan'upper` spider means. The' lower` end of'stator 42 isY supported by stationaryA journalV 82" current tiow or by absorbing heat from laminations are secured together by a plurality of rods 62 running lengthwise and clamping the laminations to annular head piece 64.

As indicated in Fig. 3, laminations 60 are provided with deep slots on opposite sides thereof identified as 66 through which the winding, electromagentically coupled to the laminations, is wound. As indicated both in Fig. 3 and further in Figs. 2A and 2B, said winding is a continuous loop of flat strip material wound in the generally elliptical shape with the elongated axis of the ellipse substantially co-axial with the center of the stator and tachometer generator. Preferably, the flat strip Winding extends from side-to-side in the slots 66 and the winding is continuous with insulation .material therebetween throughout its continuous wrapping in the elliptical form. Insulation, of course, sufficiently overlaps the edges of the windings so that the electrical current generated in the individual turns is not short-circuited by the metal of the laminations 6i). As more particularly illustrated in Figs. 2A and 2B, the outer windings of the vcontinuous loops are somewhat narrowed in a stair-step fashion so that the outer turns generally conform to the diameter of the circle circumscribing the laminations 60. The outer turns are correspondingly thickened to maintain substantially constant the cross-sectional area of each turn. The continuous winding is indicated generally by the numeral 68 and the insulation therebetween by 70. The entire assembly of head sections 72 and 64, as well as stacked laminations 60 and the winding 68, are enclosed in a non-magnetic covering 74, such as stainless steel, that extends above and below the head sections. While not shown in the drawings, the inner end of the winding 68 is brazed to one of the head pieces so that the entire case forms a ground connection and only a single terminal, indicated as 76, passes to the exterior of pressure head section 44 through a conduit '78.

For the purpose of centering stator assembly 42, relative to rotor member 40, the upper end of stator 42, or specifically, the head -section 72, is secured to pressure head 44 through an elongated journal bearing section identified as 80. The bottom portion of the stator includes a journal portion 82 that is secured to the lower head 64 which in turn forms a bearing member for the lower part of rotor 40. For the purpose of preventing undue -wear on both the journal 82 and the bearing 80, the rotating parts of rotor member 40 are provided with rubber bushings respectively identified as 84 and 86. In the arrangement shown in Fig. 2A, the stator member is subjected to a hydrostatic pressure equal to that of the drilling uid in the annular space 38 surrounding the tachometer generator 17. As there shown, the interior of the stator member includes a head space 88 that is filled with an insulating oil and the pressure Ythereon is maintained equal to ambient pressure through the bellows arrangement 90, which in turn is immersed in the drilling fluid in the outer chamber identified as 92. The pressure in said outer chamber is maintained substantially the same as that of the drilling uid by the orifice 94 formed in the closure cap 96 for pressure head 44. The chamber 92 will be lled with drilling mud, or a mixture of mud and oil, as it will happen, and the orifice 94 is to prevent rapid movement, or interchange of pressure in or out of space 92. The device is essentially a balancing of hydrostatic pressures, plus allowance for thermal expansion of the oil in the generator stator when heated by the borehole environment. As indicated in Fig. 2A, insulated electrical conductor '76 passes through a bushing member 98 and conduit 78.

Referring to the illustrated construction of the rotor element 40 of the tachometer generator, it is to be observed that said rotor element 40 is substantially immersed in the drilling fluid so that tight seals to exclude the drilling uid are not required. As mentioned above, the rotor comprises an annular permanent magnet member 48, formed, for example, of one or more paralleled rings ofAlnico, and held in vertical and annular align- .ment by an outer nonmagnetic member 100, which in a D.C. source, thus polarizing the annular Alnico magnets.

Rotor member 40 is driven by the jaw coupling or key member 54, which is coupled to turbine shaft 30 by slot 53 in bushing 51. A thrust bearing, such as ball bearing 103, carries the weight of rotor 40 and as shown in Fig. 2B, the inner and outer axial surfaces of drive collar 83 are respectively guided in rubber bearings. The inner surface of collar 83 has a rubber sleeve insert 84 that bears on journal 82, while the outer surface of said collar is guided by insert 85 in support member 59.

As mentioned above, shaft 30 directly drives drill bit 1l. Thus, upon rotation of the polarized permanent magnet element 43, there is established ow of current within the single elongated winding 68 which will be an A.C. signal whose frequency is directly proportional to the speed of rotation of the permanent magnet eld. The strength of such A.C. signal is of course determined by the total magnetic ux of the permanent magnets, the spacing between the pole faces and the stator, and the number and size of conductor turns on the stator. In the present arrangement, the internal impedance of the stator itself is designed to have a very low value to match as nearly as possible the earth impedance, to obtain maximum power in the signal actually transmitted.

With the foregoing construction of our inside-out generator, there is provided a maximum length of flux path within the annular permanent magnet rotor in a minimum of cylindrical volume, resulting in greater magnetic stability of the rotor. Further, the cylindrically solid stator provides a construction that can be more readily sealed lagainst hydraulic pressure and an electrical -winding that can be readily connected to a transmission'line through'a stationary contact, rather than through a slip ring connection.

The central construction of the stator permits the winding to have a maximum amount of copper with a minimum length so that the internal impedance is kept low. This arrangement also furnishes a short and therefore low-reluctance magnetic path through the stator.

Referring now to Fig. 4, 'there is shown an alternative method of winding stator 42. This view is similar to Fig. 3 but shows the use of square, or rectangular, insulated wire laid in the slots 66A. By this arrangement, there is made possible a greater number of turns in the same winding space and a somewhat more eflicient use of the slot space and that portion of the winding that fills the subtended arc completing the circle of the stator cylinder. As indicated in exaggerated form for clearer understanding, the sides of slots 66A may be slightly tapered outwardly so that each layer of turns can be more readily fed into the slots without danger of breaking the insulation covering the wire. Alternatively, four bare, square wires may be bundled to` gether, in contact with each other. This bundle is then wrapped with a tape, or sleeved with insulating material to form a single exible conductor that forms the continuous winding of the coil.

From the foregoing description, it will be apparent that the inside-out construction of the generator is also Vthoserskillecl in the art.

useful` in, generating electricallsignals; withini along: nar-A row borehole. containing liquid., to. indicate f physical con'- ditionsother thanturbinespeed; VFor example-,f an im-` peller canu bei secured .toi the annular" rotor 'toi 'detect4 direction or speed of fluid ow. Other uses. includethef generation of an electrical signal -by said generatorinf response tov changes in temperature, pressure, orI electrical quantities indicative of a characteristic, of the earth formations through which the borehole passes.

While only a Yfew exemplilcation's' of the 'present invention havebeen shownvanddescribed, various modif cations and changes. therein will become apparent to ing a rotatable element directly coupled to ythe^upperI endy of' a drivev shaft of a hydraulic turbine, saidrotatableelement beingdrivably coupled to an annular permanent: magnet rotor member'extendingwaV substantialv distance upwardly intoatfluid supplying drill pipe fromv the upper endof saididrive'A shaft, a cylindrical.V stator member centrally'disposed within and! circumferentially surrounded'l by said annular permanent magnet rotor member, means, for' maintaining said* cylindricalv stator l member-under hydraulic pressure sutcient'fto` counterbal'ancetthe' pressure of` a drilling iluiddriving saidl turbine, electrical winding. means-within said--stator mem ber and: electromagnetically coupled with saidpermanent magnet rotor member, andV means for interconnecting anvelectric'al transmission lineewith: onev end of saidY electrical windingmeans' within said stator member to transmit to` the earths; surface anelectrical-signal corresponding to the speed'ofrrotation oi'said'tur-A bine and ai drillbitsecuredito'the opposite` end'offsaid drive shaft.k -Y

2. Apparatus lfor generating :an alternatingcurrent` in response to a physical icondition measuredy attihe botto-rn of a well borewihiley said Well bore .is 'being drilled," comprising a rotorzelementz mounted within afdrillpipe extending to the surface Iof theearth. and'v adapted tol be drivenwin responsepto aphysica-l c'onditionto bedetected,

' said rotor element including a drivev connectionsecured to anl annular Ypermanent magnet rotorA member extending a, substantial distance. axiallyuwithin saidjdrill pipe, said, drill :pipe supplying. drilling fluid under pressure to a .drill-bit at the bottom lof-said wellbore, a cylindrical` All l suchchangesfalling with-- stator member positionedsubstantially centrally in said drill pipe and within s aidannular permanentmagnetr rotori member,fmeans including a cylindrical'lc'asing surrounding. said stator member fort Yautomatically maintainingfsaid statorrmember under-hydraulic pressure s uflicient to counterbalancel the? pressure offsaid drillingjfluid in said vdrillv pipe, an insulating. fluid within said cylindrical casing, said stator membercomprising-a plurality' of parallel laminationsl positioned" transversely to the longitudinal'axis'of said statorfmember and extending substantially ooextensivelyin the {direction-ofY saidlongitudinal axis with the yprerrrlanentmagnets of; said annular rotor member, a continuous electrical coil Winding positioned in slots formed in said-laminations of 'said stator4 member YandV electromagnetically coupled with said annular'. permanent magnet rotor memhenysaid coil ,winding' comprising-a plurality of turns of an electrical conductor; offrectangular cross=section wound axially around vthe-said laminations of said stator memberwith anl electrical insulator-between each turn ofV said' electrical conductor, a single. electrical terminal interconnecting Vone end of Vsaid continuous-1 electrical coil winding` andl an antenna elec'- trodelocated outside of vsaid" sta'toir member casing to transmit to recording means positioned' at thesurface of theearthiasignal generatedin saidstator member by` rotation of said rotor member.

3 Apparatus in:v accordance j with claim 2 wherein said conductorY is a flatfstrip ofconductive material, each'v turn of-a substantial portion of-saicl Winding extending' laterally Vtlziro-ughout the widt-hfofsaid slots in said laminationsf forming saidistator. t

ll-LApparatus inV accordance with'claim 2 wherein said:

v conductor is.` formed'y of"square wireinsulated throughout its length andv said wire'includes ,a plurality of turns forming successive llayers in saidV slotsA of` said lamina-v tions forming said' stator member;

5. Apparatus in accordance with claim l'wherein the stator mem-berineludes an upper' axial extension supportedQby-spider means secured tov the drill pipe and a lower axialV extension toward'the'- driven end of said annu-lar rotor member,v said-lower extension formi-ng a radial I bearing Afor ymaintainingsaid annular rotor member radially alignedwith ysaid stator'rnemlber, and said annular lrot-or ymember includes annular bearing means adjacent its" upper end for engaging an outer circumference of said stator-member'below said spider means,V and'a lower spider-meansv secured to Ithe drill pipe'supporting,v a radial guide Ibearing andan axial fthrust'bearv ing'f'cr'said annularrotor-member.

ReferencesCited in the tile of'thispatent UNITED STATES PATENTSY 

